Adding support for Python3
What's Changed
* Migrating to python3 by mave007 in https://github.com/icann-dns/zonecheck/pull/3
New Contributors
* mave007 made their first contribution in https://github.com/icann-dns/zonecheck/pull/3
**Full Changelog**: https://github.com/icann-dns/zonecheck/compare/1.2.0...1.3.0-beta-0